Semantics and Pragmatics A free online journal that focuses on articles in semantics and pragmatics. While relatively new, it contains articles from some of the top researchers in the field.
FoLLI The association for language, logic and information, it aims 'to advance the practicing of
research and education on the interfaces between
Logic, Linguistics, Computer Science and Cognitive
Science and related disciplines.' They organise a summer school in Europe every year (ESSLLI), with advanced courses in semantics, logic, and computational linguistics.
Syntax Mailing List This is a yahoo group that focuses on topics in syntax (and occasionally semantics). Mostly it's announcements of papers but there are occasional discussions of topics of interest.
The Stanford Encyclopedia of Philosophy Offers articles on many issues in philosophy, including semantics and philosophy of language. Contains both description of key issues and by-topic bibliographies for further reading.